Current air samplers are very inefficient in collecting airborne viruses such as influenza virus, and thus their presence in breathing air is typically missed and the risk of inhalation exposure to the airborne viruses may be grossly underestimated. The ultimate goal of the project is to enable better understanding of the transmission pathways of respiratory infectious diseases and better exposure assessment methods through the development of a novel tool for efficient collection of airborne viable viruses, as such knowledge is critical to establishing effective strategies for protecting public health. Our central hypothesis is that temperature-moderated laminar-flow condensation allows Super- Efficient Sampling of nanosized Influenza virus aerosol (SESI) while maintaining viability of collected viruses. The SESI enlarges nanometer sized airborne particles to micrometer sizes without temperature extremes, and permits their collection directly into liquid. Preliminary studies showed that such a system is 40 times more effective at collecting airborne MS2 virus (diameter = 28 nm) in a viable (live) state than current devices. Three specific aims will test te hypothesis using influenza virus as a model agent: Aim 1: Develop a next-generation virus aerosol sampler that has the option to vary the temperature at the point of collection from cool (10 C) to warm (40 C) while maintaining low liquid volume of the collection media to yield a concentrated liquid sample. Aim 2: Optimize the new system for collection of viable influenza virus, through tests at varying temperatures, virus concentrations and collection media. Aim 3: Field test the performance of the optimized SESI for airborne influenza virus and compare with current standard sampler (BioSampler(r)), during winter, spring and summer. Successful development of the proposed SESI will enable accurate detection of airborne viruses in a way never accomplished before and significantly improve our scientific understanding of the transmission pathways of influenza (and other) viruses. It will also facilitate air monitoring durig respiratory virus outbreaks, and setting evidence-based policies and infection control procedures that can better protect the public and susceptible individuals against exposure to infectious airborne influenza (and other) viruses.